Vitamin A

Animal Nutrition of Class 11

Synonyms. Vitamin A group includes Retinol, Retinal and Retinoic Acid. Their parent substance is -Carotene which is called a provitamin. Anti-infection vitamin, Anti-xerophthalmic vitamin.

Sources. Fish liver oils (e.g., cod liver oil), animal liver, egg yolk,  milk, and milk products, vegetables such as carrots, spinach, tomatoes. In vegetables, Vitamin A exists as a provitamin in the form of -carotenes which are yellow pigments.

Daily Requirement. About 2 mg.

Functions.

  •  It is necessary for rhodopsin of rod cells and iodopsin of cone cells of the retina of eye Rhodopsin and iodopsin are retinal pigments. Thus vitamin A promotes normal vision.
  • It is also required for the normal growth and development of lacrimal glands (tear glands).
  •  It is also essential for the maintenance of epithelial cells of skin and mucous membrane. Healthy epithelial cells do not allow infection, that is why vitamin A is also called anti infection vitamin.
  •  It promotes growth of bones and teeth.
  •  It is necessary for reproduction.
  •  Vitamin A has anti-cancer property. (vii) Retinol in the lowest oxidation state probably serves as hormone.

Deficiency Symptoms (Effects of Deficiency)

  •  Night blindness (Nyctalopia)
  • Xerophthalmia- Drying of eyeball.
  • Dermatosis- Dry and scaly skin.
  • Keratomalacia-Corneal epithelium becomes keratinized and opaque and may become softened and ulcerated.

Destroyed by : Strong light.

Hypervitaminosis A. If vitamin A is taken in excess it causes headache, nausea (discomfort preceeding vomiting), vomiting, drowsiness, loss of appetite and painer in bones.

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